11-24-2006
test Null variable
hi forum
i beginning with script and i want test un null variable in a schell
i just don t know the syntax here is a litle example
y=test
echo $y
unset y
echo $y (so here Y = Null)
if Y=Null
then
echo "y is null"
exit
fi
i have try
if [ !$y ]
but i have the error
test: argument expected
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ECHO(3) 1 ECHO(3)
echo - Output one or more strings
SYNOPSIS
void echo (string $arg1, [string $...])
DESCRIPTION
Outputs all parameters.
echo is not actually a function (it is a language construct), so you are not required to use parentheses with it. echo (unlike some other
language constructs) does not behave like a function, so it cannot always be used in the context of a function. Additionally, if you want
to pass more than one parameter to echo, the parameters must not be enclosed within parentheses.
echo also has a shortcut syntax, where you can immediately follow the opening tag with an equals sign. Prior to PHP 5.4.0, this short syn-
tax only works with the short_open_tag configuration setting enabled.
I have <?=$foo?> foo.
PARAMETERS
o $arg1
- The parameter to output.
o $...
-
RETURN VALUES
No value is returned.
EXAMPLES
Example #1
echo examples
<?php
echo "Hello World";
echo "This spans
multiple lines. The newlines will be
output as well";
echo "This spans
multiple lines. The newlines will be
output as well.";
echo "Escaping characters is done "Like this".";
// You can use variables inside of an echo statement
$foo = "foobar";
$bar = "barbaz";
echo "foo is $foo"; // foo is foobar
// You can also use arrays
$baz = array("value" => "foo");
echo "this is {$baz['value']} !"; // this is foo !
// Using single quotes will print the variable name, not the value
echo 'foo is $foo'; // foo is $foo
// If you are not using any other characters, you can just echo variables
echo $foo; // foobar
echo $foo,$bar; // foobarbarbaz
// Some people prefer passing multiple parameters to echo over concatenation.
echo 'This ', 'string ', 'was ', 'made ', 'with multiple parameters.', chr(10);
echo 'This ' . 'string ' . 'was ' . 'made ' . 'with concatenation.' . "
";
echo <<<END
This uses the "here document" syntax to output
multiple lines with $variable interpolation. Note
that the here document terminator must appear on a
line with just a semicolon. no extra whitespace!
END;
// Because echo does not behave like a function, the following code is invalid.
($some_var) ? echo 'true' : echo 'false';
// However, the following examples will work:
($some_var) ? print 'true' : print 'false'; // print is also a construct, but
// it behaves like a function, so
// it may be used in this context.
echo $some_var ? 'true': 'false'; // changing the statement around
?>
NOTES
Note
Because this is a language construct and not a function, it cannot be called using variable functions.
SEE ALSO
print(3), printf(3), flush(3), Heredoc syntax.
PHP Documentation Group ECHO(3)